The present invention relates to a pole structure in a permanent magnet type electric rotating machine, which is composed of a stator having a salient-pole concentrated winding, and a rotor having a permanent magnet arranged and fixed in a circumferential direction, and which is suitably used particularly for a hybrid electric vehicle. The invention further relates to a hybrid electric vehicle using such a permanent magnet type electric rotating machine.
Generally, as regards an electric rotating machine for an electric vehicle, a so-called vehicle wheel motor for an electric vehicle has been used as a driving source for an industrial vehicle such as a load carrier. For example, one disclosed in JP-A-8-99538 has already been known. Such a vehicle wheel motor includes a permanent magnet type electric rotating machine having a salient-pole concentrated winding. According to this technology, to suppress the generation of noise at an extremely low speed, a ratio between the number of magnetic poles for a rotor and the number of slots for a stator is set equal to a predetermined value. The above conventional technology provides an exemplary structure where the number of magnetic poles for the rotor is 8, and the number of slots for the stator is 12. However, such a technology is designed to suppress the generation of noise by performing so-called skewing magnetization in a surface magnet type electric rotating machine having a magnet disposed on the surface of the rotor. Although the fixing of the magnet to the rotor surface is not specified, it can be understood from its structure that the magnet is fixed by adhesive or the like.
For example as disclosed in JP-A-11-299199, a permanent magnet type electric rotating machine presented by the present inventors and an electric vehicle using such an electric rotating machine have been known. This electric rotating machine is different from the machine of the invention comprising a stator having a salient-pole concentrated winding in that a so-called distributed winding having three-phase 8 poles/48 slots (1:6) is set for a stator iron core. An angle θ (mechanical angle) between the circumferential width of each permanent magnet in the outer peripheral surface of the stator side and the shaft center of the rotor is set at θ≈n×τs+16/P (is a natural number), where a slot pitch of the stator is τs (mechanical angle, as shown in FIG. 1), and the number of poles is P.
In addition, as regards an electric motor for other than vehicle, for example as disclosed in JP-A-7-255138, there is available a permanent magnet type electric synchronous rotating machine structured to have the number of rotor poles set at 6, and the number of stator slots set at 9. However, this technology uses a magnet shaped like a convex lens in section, and a triangular groove for preventing the leakage of magnetic fluxes is provided between the poles.